My company is looking for an alternate solution for posting files to
share with our clients.

Currently we're using Basecamp and it is good, but has it’s
limitations. We like the ‘forum’ nature of it but it good do with some
tweaks. I think the biggest downfall (forgive me if I’m wrong, I have
only the most basic understanding of it) is the presentation layer. We
should be trying to display as much work on screen as we possibly can,
rather than the continual “download and open” process.